The Greater Portland METRO is a regional public transportation system in Southern Maine. Operated by the Greater Portland Transit District, a transit district comprising Portland, Westbrook, Falmouth, Yarmouth, Freeport, and Brunswick, the system also covers Gorham and the Maine Mall portion of South Portland. METRO was formed in 1966. METRO is Maine's largest public transportation agency. The transit system's annual ridership was 1,850,686 in 2017.